1. Field of the Invention
This invention relates to a novel nanoporous membrane catalyst and a process of production of the nanoporous membrane catalyst, and more particularly, this invention relates to a nanoporous catalyst of high reactant conversion rates and a process of production of the catalyst using atomic layer deposition (ALD).
2. Background of the Invention
Selective catalytic oxidation (SCO) remains one of the most desirable and elusive technologies for chemical and fuels processing and environmental protection. Industrial catalysts are generally high surface area substrates onto which an active component is dispersed in the form of very small particles. These particles have typical dimensions of 1 nanometer (nm) to 20 nm and are often referred to as nanoparticles.
Nanoporous catalytic materials, predominantly in the form of zeolites, have gained wide acceptance as industrial catalysts for oil refining, petrochemistry, and organic synthesis, particularly for molecules with kinetic diameters below 1 nm.
There has been little prior work in which nanoporous alumina has been used as a catalyst or as a support for catalytic nanoclusters. Rather, the anodic alumina, as a film or thin shell on an aluminum base, was used directly as a catalyst. Subsequently, oxide catalysts were supported on these anodic alumina films, but these works did not employ membrane catalysts.
The use of anodic alumina membranes for deposition of metal nanoparticles into the pores from colloidal solution has been shown in: T. Hanaoka, H. P. Kormann, M. Kroell, T. Sawitowski, G. Schmid, Three-Dimensional Assemblies Of Gold Colloids In Nanoporous Alumina Membranes, Eur. J. Inorg. Chem., 807-812 (1998). Similarly, the use of AAO materials for anchoring metal complexes on the pore walls was shown in: P. Braunstein, H. P. Kormann, W. Meyer-Zaika, R. Pugin, and G. Schmid, Strategies For The Anchoring Of Metal Complexes, Clusters, And Colloids Inside Nanoporous Alumina Membranes, Chem. Eur. J. 6, 4637-4646 (2000). However, the membranes employed (250 nm pore diameter) were well beyond the nanoscale target dimensions necessary to effect reactions with 1 nm to 10 nm size molecules.
U.S. Pat. No. 6,740,143 awarded to Corbin, et al. on May 25, 2004 discloses a method for the synthesis of nanoporous carbon membranes. The method entails pyrolysis of selected polymers on porous substrates to produce thin mixed matrix carbon film with pores. The carbon film facilitates the separation of small molecules from a reaction liquor.
U.S. Pat. No. 6,471,745 awarded to Foley, et al. on Oct. 29, 2002 discloses catalytic membranes comprising highly-dispersed, catalytically-active metals in nanoporous carbon membranes and a single-phase process to produce the membranes.
U.S. Pat. No. 4,921,823 awarded to Furneaux, et al. on May 1, disclosed a method for the synthesis of nanoporous carbon membranes. The method discloses a porous anodic aluminum oxide membrane catalyst support with pore sizes of 80 nm.
None of the aforementioned patents discloses a nanoporous membrane with pore sizes at least as small as 10 nm and a process for making such nanoporous membranes. In addition, none of these patents discloses a method for creating catalysts of vanadia with nanopores.
A need exists in the art for nanoporous membranes with pore sizes at least as small as 10 nm and a process to make them. Such materials can provide a higher degree of reaction selectivity, greater complexity and the use of a range of catalysts, including nanoporous vanadia catalysts.